The medical fraternity has been examining cases of myocarditis and pericarditis that have been sporadically linked with COVID-19 vaccines. Mostly reported in males under 40, these cases are rare yet noteworthy. While these cases are primarily seen after the second dose, they have also been reported post the first and even third or fourth doses.

Understanding myocarditis and pericarditis

Researchers have identified a certain correlation between these rare side effects and COVID-19 vaccines. Myocarditis and pericarditis, inflammations of the heart muscle and the sac-like tissue surrounding the heart muscle respectively, can occur together or separately. While vaccines may not be the cause for all post-vaccination cases, COVID-19 can also induce these conditions.

Demographics and risk

Statistical data suggests the highest risk group is people aged between 16 to 30, particularly males. However, booster doses have shown less risk when compared to the second dose of the primary course. Cases reported to the Therapeutic Goods Administration (TGA) offer an up-to-date record of the situation.

Surprisingly, the original formulation of Moderna has shown a slightly higher link to myocarditis cases compared to Pfizer’s, particularly in individuals under 40 receiving their second dose. It’s important to note that AstraZeneca and Novavax also show a minimal increased risk.

Brands and severity

However, no evidence suggests a more severe risk of myocarditis or pericarditis with a specific brand. Most cases linked to COVID-19 vaccination have been mild with patients recovering rapidly.

Age factor and risk mitigation

Children aged 5 to 11 years appear to have a lower risk compared to adolescents. The risk also seems to decrease after a booster compared to the primary course. For children aged between 6 months to less than 5 years, there is no clear risk of these conditions post vaccination. A longer interval between doses might slightly reduce the risk while also improving vaccine protection.

Conclusive study

As of February 2023, the full nature of the risk of myocarditis or pericarditis following booster doses with Pfizer or Moderna’s bivalent original/Omicron vaccines has not been fully characterised.

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References
Yauhara J, Masuda K, Aikawa T, et al. Myopericarditis after COVID-19 mRNA vaccination among adolescents and young adults: a systematic review and meta-analysis. JAMA Pediatrics 2023;177:42-52.
Ling RR, Ramanathan K, Tan FL, et al. Myopericarditis following COVID-19 vaccination and non-COVID-19 vaccination: a systematic review and meta-analysis. Lancet Respir Med 2022;10:679-88.
Pillay J, Gaudet L, Wingert A, et al. Incidence, risk factors, natural history, and hypothesised mechanisms of myocarditis and pericarditis following COVID-19 vaccination: living evidence syntheses and review. BMJ 2022;378:e069445.
Yechezkel M, Mofaz M, Painsky A, et al. Safety of the fourth COVID-19 B